Unfortunately not. Some of NCH's products do have an API/SDK (for example IVM), but Axon does not provide such an interface to control/modify the program.
However, you can still control some things in Axon. For example, using the registry it is possible to change settings, extensions etc. in real-time and also view Axon's log in real-time.
Other than that however, it is not really possible to actually modify the program and extend it like IVM.
I should note that NCH is more than willing to modify Axon to fit your needs, and allow you to customize the UI etc. for a fee. I believe they will also reduce the development fee if you allow NCH to use the new features you requested in the next public versions of Axon.
For more information see: http://www.nch.com.au/development/index.html
and http://www.nchsoftware.com/software/customize.html (for GUI customization)
Also, your question isn't technically "Pre Sales" as Axon is currently free of charge 